1221591 has 8 divisors (see below), whose sum is σ = 1861504. Its totient is φ = 698040.

The previous prime is 1221589. The next prime is 1221593. The reversal of 1221591 is 1951221.

1221591 = 29² + 30² + ... + 154².

It is an interprime number because it is at equal distance from previous prime (1221589) and next prime (1221593).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1221591 - 2¹ = 1221589 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21), and also a Moran number because the ratio is a prime number: 58171 = 1221591 / (1 + 2 + 2 + 1 + 5 + 9 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221593) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 29065 + ... + 29106.

It is an arithmetic number, because the mean of its divisors is an integer number (232688).

2^1221591 is an apocalyptic number.

1221591 is a deficient number, since it is larger than the sum of its proper divisors (639913).

1221591 is an equidigital number, since it uses as much as digits as its factorization.

1221591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58181.

The product of its digits is 180, while the sum is 21.

The square root of 1221591 is about 1105.2560789247. The cubic root of 1221591 is about 106.8994017672.

The spelling of 1221591 in words is "one million, two hundred twenty-one thousand, five hundred ninety-one".